Full Idea
The four essential properties of modules are: encapsulation (information doesn't flow, as in the persistence of illusions); inaccessibility (unreportable); domain specificity (they have private concepts); innateness (genetically preprogrammed).
Gist of Idea
Modules have encapsulation, inaccessibility, private concepts, innateness
Source
Jerry A. Fodor (In a Critical Condition [2000], Ch.11)
Book Reference
Fodor,Jerry A.: 'In Critical Condition' [MIT 2000], p.127
A Reaction
If they have no information flow, and are unreportable and private, this makes empirical testing of Fodor's hypothesis a little tricky. He must be on to something, though.